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  • Preprocessor #define vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • Dynamically adjust padding on an image?

    - by Cory
    What I'm basically attempting to do is dynamically change a padding value for a scrubber image based on player position data provided by an app. I have been able to leverage the provided number to dynamically increase the width of a progress overlay image and create a progress bar, but I would like a scrubber diamond at the leading edge of the progress bar. To do this, I have positioned the scrubber diamond at the same starting point as the progress overlay and would like to increase the padding on the diamond at the same rate as the width is increasing for the progress overlay, allowing them to pace each other with the scrubber diamond moving as the song plays. Any help with the script necessary to manipulate padding-left dynamically would be very much appreciated. var progress = Ecoute.playerPosition(); var width = 142.5 / length * progress + 1.63; EcouteSel('Progression').width = width.toString(); EcouteSel('Scrubber').style('padding-left', 'width'); We define progress as the player position, width as a function of the progress and then apply that function to the ID applied to the progress over lay image. But how do I accomplish that for padding-left? style.paddingLeft ...based functions have broken the controller outright. I'm at a loss and any help would be appreciated.

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  • variables in abstract classes C++

    - by wyatt
    I have an abstract class CommandPath, and a number of derived classes as below: class CommandPath { public: virtual CommandResponse handleCommand(std::string) = 0; virtual CommandResponse execute() = 0; virtual ~CommandPath() {} }; class GetTimeCommandPath : public CommandPath { int stage; public: GetTimeCommandPath() : stage(0) {} CommandResponse handleCommand(std::string); CommandResponse execute(); }; All of the derived classes have the member variable 'stage'. I want to build a function into all of them which manipulates 'stage' in the same way, so rather than defining it many times I thought I'd build it into the parent class. I moved 'stage' from the private sections of all of the derived classes into the protected section of CommandPath, and added the function as follows: class CommandPath { protected: int stage; public: virtual CommandResponse handleCommand(std::string) = 0; virtual CommandResponse execute() = 0; std::string confirmCommand(std::string, int, int, std::string, std::string); virtual ~CommandPath() {} }; class GetTimeCommandPath : public CommandPath { public: GetTimeCommandPath() : stage(0) {} CommandResponse handleCommand(std::string); CommandResponse execute(); }; Now my compiler tells me for the constructor lines that none of the derived classes have a member 'stage'. I was under the impression that protected members are visible to derived classes? The constructor is the same in all classes, so I suppose I could move it to the parent class, but I'm more concerned about finding out why the derived classes aren't able to access the variable. Also, since previously I've only used the parent class for pure virtual functions, I wanted to confirm that this is the way to go about adding a function to be inherited by all derived classes.

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  • How to implement a grapher in C#

    - by iansinke
    So I'm writing a graphing calculator. So far I have a semi-functional grapher, however, I'm having a hard time getting a good balance between accurate graphs and smooth looking curves. The current implementation (semi-pseudo-code) looks something like this: for (float i = GraphXMin; i <= GraphXMax; i++) { PointF P = new PointF(i, EvaluateFunction(Function, i) ListOfPoints.Add(P) } Graphics.DrawCurve(ListOfPoints) The problem with this is since it only adds a point at every integer value, graphs end up distorted when their turning points don't fall on integers (e.g. sin(x)^2). I tried incrementing i by something smaller (like 0.1), which works, but the graph looks very rough. I am using C# and GDI+. I have SmoothingMethod set to AntiAlias, so that's not the problem, as you can see from the first graph. Is there some sort of issue with drawing curves with a lot of points? Should the points perhaps be positioned exactly on pixels? I'm sure some of you have worked on something very similar before, so any suggestions? While you're at it, do you have any suggestions for graphing functions with asymptotes? e.g. 1/x^2 P.S. I'm not looking for a library that does all this - I want to write it myself.

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  • PHP: Extract direct sub directory from path string

    - by Nebs
    I need to extract the name of the direct sub directory from a full path string. For example, say we have: $str = "dir1/dir2/dir3/dir4/filename.ext"; $dir = "dir1/dir2"; Then the name of the sub-directory in the $str path relative to $dir would be "dir3". Note that $dir never has '/' at the ends. So the function should be: $subdir = getsubdir($str,$dir); echo $subdir; // Outputs "dir3" If $dir="dir1" then the output would be "dir2". If $dir="dir1/dir2/dir3/dir4" then the output would be "" (empty). If $dir="" then the output would be "dir1". Etc.. Currently this is what I have, and it works (as far as I've tested it). I'm just wondering if there's a simpler way since I find I'm using a lot of string functions. Maybe there's some magic regexp to do this in one line? (I'm not too good with regexp unfortunately). function getsubdir($str,$dir) { // Remove the filename $str = dirname($str); // Remove the $dir if(!empty($dir)){ $str = str_replace($dir,"",$str); } // Remove the leading '/' if there is one $si = stripos($str,"/"); if($si == 0){ $str = substr($str,1); } // Remove everything after the subdir (if there is anything) $lastpart = strchr($str,"/"); $str = str_replace($lastpart,"",$str); return $str; } As you can see, it's a little hacky in order to handle some odd cases (no '/' in input, empty input, etc). I hope all that made sense. Any help/suggestions are welcome.

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  • Making a visual bar timer for iPhone

    - by Ohmnastrum
    I've looked up all results for progress bars and changing the width of an image but it only refers to scaling, and the progress bars aren't customizable so that they fit other functions or design schemes... unless I missed that part. I'm trying to make a bar timer that crops off of the right over a period of time. I tried using an NStimer so that it would subtract from a value each time its function is called. the Timerbar function gets called as a result of another timer invalidating and it works. What doesn't work is that the width isn't changing just the position. further more I keep getting values like Inf and 0 for power and pwrBarWidth I was sure that the changes would occur when Mult was plugged into the equation. it seems like casting mult as an int is causing problems but i'm not sure exactly how. int pwrBarMaxWidth = 137; int pwrBarWidth 0; int limit = 1; float mult; float power = 0; -(void) Timerbar:(NSTimer *)barTimer { if(!waitForPlayer) { [barTimer invalidate]; } if(mult > 0.0) { mult -= 0.001 * [colorChoices count]; if(mult < 0.0) { mult = 0.0; } } power = (mult * 10) / pwrBarMaxWidth; pwrBarWidth = (int)power % limit; // causes the bar to repeat after it reaches a certain point //At this point however the variable Power is always "inf" and PwrBarWidth is always 0. [powerBar setBounds:CGRectMake(powerBar.frame.origin.x, powerBar.frame.origin.y,pwrBarWidth,20)]; //supposed to change the crop of the bar } Any reason why I'm getting inf as a value for power, 0 as a value for pwrBarWidth, and the bar itself isn't cropping? if this question is a bit vague i'll provide more information as needed.

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  • Zend Framework-where do calls to my methods go? Controller of Model?

    - by Joel
    Hi guys, I'm confused about exactly what I should have in my controller and what in my method. Specifically, I have this in the action method: public function upcomingshowsAction() { $gcal = $this->_validateCalendarConnection(); $uncleanedFeedArray = $this->_getCalendarFeed($gcal); $finishedFeedArray = $this->_cleanFeed($uncleanedFeedArray); $this->view->googleArray = $finishedFeedArray; } And then (incorrectly I know), I have my methods still in the bottom of my controller. So what I'm wondering, is for those methods in the upcomingshowsAction method, should all the actual methods just be in one model and then I'd have something like this: public function upcomingshowsAction() { $finishedFeedArray = new Application_Model_calendarModelPage(); $this->view->googleArray = $finishedFeedArray; } And then something like this in the model: class Application_Model_CalendarModelPage { $gcal = $this->_validateCalendarConnection(); $uncleanedFeedArray = $this->_getCalendarFeed($gcal); $finishedFeedArray = $this->_cleanFeed($uncleanedFeedArray); public functions { ... ... ... } } Am I on the right track here? Thanks!

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  • Jquery animate negative top and back to 0 - starts messing up after 3rd click

    - by Daniel Takyi
    The site in question is this one: http://www.pickmixmagazine.com/wordpress/ When you click on one of the posts (any of the boxes) an iframe will slide down from the top with the content in it. Once the "Home" button in the top left hand corner of the iframe is clicked, the iframe slides back up. This works perfectly the first 2 times, on the 3rd click on of a post, the content will slide down, but when the home button is clicked, the content slides back up normally but once it has slid all the way up to the position it should be in, the iframe drops straight back down to where it was before the home button was clicked, I click it again and then it works. Here is the code I've used for both sliding up and sliding down functions: /* slide down function */ var $div = $('iframe.primary'); var height = $div.height(); var width = parseInt($div.width()); $div.css({ height : height }); $div.css('top', -($div.width())); $('.post').click(function () { $('iframe.primary').load(function(){ $div.animate({ top: 0 }, { duration: 1000 }); }) return false; }); /* slide Up function */ var elm = parent.document.getElementsByTagName('iframe')[0]; var jelm = $(elm);//convert to jQuery Element var htmlElm = jelm[0];//convert to HTML Element $('.homebtn').click(function(){ $(elm).animate({ top: -height }, { duration: 1000 }); return false; })

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  • zend-framework doctrine, and mvc pattern: what should connect data between models and forms?

    - by Skirmantas
    I am learning Zend Framework and Doctrine. I am wondering what is the best practice to connect forms to models and vice versa. I don't know where I should put my code. I have seen in Zendcast video tutorials where author creates methods like mapFormToRecord and mapRecordToForm in form class. Well I guess it is very handy when form is sophisticated and uses many records. Is it a good practice? I somehow believe that form-class should not need to know about data-records. And sometimes we might have model which is used in many forms. So It would be handy to have few functions in that model which would help to prepare data for forms. For example to give an array of id=name pairs so that it might be used in Zend_Form_Element_Select. However I would like to have a consistency. So I don't want to put this code nor in model nor in form because on different situations I act different. So only controller is what is left to deal it. However this will result in code duplication if one form will be used more than in one controller. Moreover controller gets bloated if form is not from the simple ones. Or maybe there is a consistent pattern in those data conversions between forms and models? I think that there is. At least in my simple cases. So maybe a separate class could be a solution? Where should I put such class and how should I name it? Another question: Zend_Form has validators and filter. Doctrine has validators and filters too. Which do we use and when? What is your way of dealing the connections between forms and models? (Sorry if it was hard for you to read my text. I don't have enough knowledge of English language to express myself freely)

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  • What wrapper class in C++ should I use for automated resource management?

    - by Vilx-
    I'm a C++ amateur. I'm writing some Win32 API code and there are handles and weirdly compositely allocated objects aplenty. So I was wondering - is there some wrapper class that would make resource management easier? For example, when I want to load some data I open a file with CreateFile() and get a HANDLE. When I'm done with it, I should call CloseHandle() on it. But for any reasonably complex loading function there will be dozens of possible exit points, not to mention exceptions. So it would be great if I could wrap the handle in some kind of wrapper class which would automatically call CloseHandle() once execution left the scope. Even better - it could do some reference counting so I can pass it around in and out of other functions, and it would release the resource only when the last reference left scope. The concept is simple - but is there something like that in the standard library? I'm using Visual Studio 2008, by the way, and I don't want to attach a 3rd party framework like Boost or something.

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  • Comparing objects and inheritance

    - by ereOn
    Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

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  • Member function overloading/template specialization issue

    - by Ferruccio
    I've been trying to call the overloaded table::scan_index(std::string, ...) member function without success. For the sake of clarity, I have stripped out all non-relevant code. I have a class called table which has an overloaded/templated member function named scan_index() in order to handle strings as a special case. class table : boost::noncopyable { public: template <typename T> void scan_index(T val, std::function<bool (uint recno, T val)> callback) { // code } void scan_index(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code } }; Then there is a hitlist class which has a number of templated member functions which call table::scan_index(T, ...) class hitlist { public: template <typename T> void eq(uint fieldno, T value) { table* index_table = db.get_index_table(fieldno); // code index_table->scan_index<T>(value, [&](uint recno, T n)->bool { // code }); } }; And, finally, the code which kicks it all off: hitlist hl; // code hl.eq<std::string>(*fieldno, p1.to_string()); The problem is that instead of calling table::scan_index(std::string, ...), it calls the templated version. I have tried using both overloading (as shown above) and a specialized function template (below), but nothing seems to work. After staring at this code for a few hours, I feel like I'm missing something obvious. Any ideas? template <> void scan_index<std::string>(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code }

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  • How to convert a lambda to an std::function using templates

    - by retep998
    Basically, what I want to be able to do is take a lambda with any number of any type of parameters and convert it to an std::function. I've tried the following and neither method works. std::function([](){});//Complains that std::function is missing template parameters template <typename T> void foo(function<T> f){} foo([](){});//Complains that it cannot find a matching candidate The following code does work however, but it is not what I want because it requires explicitly stating the template parameters which does not work for generic code. std::function<void()>([](){}); I've been mucking around with functions and templates all evening and I just can't figure this out, so any help would be much appreciated. As mentioned in a comment, the reason I'm trying to do this is because I'm trying to implement currying in C++ using variadic templates. Unfortunately, this fails horribly when using lambdas. For example, I can pass a standard function using a function pointer. template <typename R, typename...A> void foo(R (*f)(A...)) {} void bar() {} int main() { foo(bar); } However, I can't figure out how to pass a lambda to such a variadic function. Why I'm interested in converting a generic lambda into an std::function is because I can do the following, but it ends up requiring that I explicitly state the template parameters to std::function which is what I am trying to avoid. template <typename R, typename...A> void foo(std::function<R(A...)>) {} int main() { foo(std::function<void()>([](){})); }

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  • Programmatically setup a PEAP connection in Windows Mobile

    - by tomlog
    I have been working on this for a few days and this is doing my head in: Our application is built using the .NET Compact Framework 2.0 and running on Windows Mobile 5 & 6 devices. We can set the WLAN connection of the device programmatically using the Wireless Zero Config functions (described here: msdn.microsoft.com/en-us/library/ms894771.aspx), most notably the WZCSetInterface function which we pinvoke from our application. This works fine for WEP and WPA-PSK connections. In a recent effort to add support for WPA2 networks we decided to modify the code. We have successfully added support for WPA2 which uses a certificate for the 802.1x authentication by setting the correct registry settings before calling WZCSetInterface. Now we want to do the same for WPA2 using PEAP (MS-CHAPv2) authentication. When manually creating such a connection in Windows Mobile the user will be prompted to enter the domain/user/password details. In our application we will have those details stored locally and want to do this all programmatically without any user intervention. So I thought going along the same route as the certificate authentication, setting the correct registry entries before calling WZCSetInterface. The registry settings we set are: \HKCU\Comm\EAP\Config\[ssid name] Enable8021x = 1 (DWORD) LastAuthSuccessful = 1 (DWORD) EapTypeId = 25 (DWORD) Identity = "domain\username" (string) Password = binary blob containing the password that is encrypted using the CryptProtectData function (described here: msdn.microsoft.com/en-us/library/ms938309.aspx) But when these settings are set and I call WZCSetInterface with the correct parameters, it still prompts me with the User Logon dialog asking for the domain/username/password. Has anyone got an idea what I need to do to prevent the password dialog from appearing and connect straight away with the settings stored in the registry?

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  • calling constructor of the class in the destructor of the same class

    - by dicaprio
    Experts !! I know this question is one of the lousy one , but still I dared to open my mind , hoping I would learn from all. I was trying some examples as part of my routine and did this horrible thing, I called the constructor of the class from destructor of the same class. I don't really know if this is ever required in real programming , I cant think of any real time scenarios where we really need to call functions/CTOR in our destructor. Usually , destructor is meant for cleaning up. If my understanding is correct, why the compiler doesn't complain ? Is this because it is valid for some good reasons ? If so what are they ? I tried on Sun Forte, g++ and VC++ compiler and none of them complain about it. using namespace std; class test{ public: test(){ cout<<"CTOR"<<endl; } ~test() {cout<<"DTOR"<<endl; test(); }};

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  • using threads in menu options

    - by vbNewbie
    I have an app that has a console menu with 2/3 selections. One process involves uploading a file and performing a lengthy search process on its contents, whilst another process involves SQL queries and is an interactive process with the user. I wish to use threads to allow one process to run and the menu to offer the option for the second process to run. However you cannot run the first process twice. I have created threads and corrected some compilation errors but the threading options are not working correctly. Any help appreciated. main... Dim tm As Thread = New Thread(AddressOf loadFile) Dim ts As Thread = New Thread(AddressOf reports) .... While Not response.Equals("3") Try Console.Write("Enter choice: ") response = Console.ReadLine() Console.WriteLine() If response.Equals("1") Then Console.WriteLine("Thread 1 doing work") tm.SetApartmentState(ApartmentState.STA) tm.IsBackground = True tm.Start() response = String.Empty ElseIf response.Equals("2") Then Console.WriteLine("Starting a second Thread") ts.Start() response = String.Empty End If ts.Join() tm.Join() Catch ex As Exception errormessage = ex.Message End Try End While I realize that a form based will be easier to implement with perhaps just calling different forms to handle the processes.But I really dont have that option now since the console app will be added to api later. But here are my two processes from the menu functions. Also not sure what to do with the boolean variabel again as suggested below. Private Sub LoadFile() Dim dialog As New OpenFileDialog Dim response1 As String = Nothing Dim filepath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) dialog.InitialDirectory = filepath If dialog.ShowDialog() = DialogResult.OK Then fileName = dialog.FileName ElseIf DialogResult.Cancel Then Exit Sub End If Console.ResetColor() Console.Write("Begin Search -- Discovery Search, y or n? ") response1 = Console.ReadLine() If response1 = "y" Then Search() ElseIf response1 = "n" Then Console.Clear() main() End If isRunning = False End Sub and the second one Private Shared Sub report() Dim rptGen As New SearchBlogDiscovery.rptGeneration Console.WriteLine("Tread Process started") rptGen.main() Console.WriteLine("Thread Process ended") isRunning = False End Sub

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  • Recommended approach for error handling with PHP and MYSQL

    - by iama
    I am trying to capture database (MYSQL) errors in my PHP web application. Currently, I see that there are functions like mysqli_error(), mysqli_errno() for capturing the last occurred error. However, this still requires me to check for error occurrence using repeated if/else statements in my php code. You may check my code below to see what I mean. Is there a better approach to doing this? (or) Should I write my own code to raise exceptions and catch them in one single place? What is the recommended approach? Also, does PDO raise exceptions? Thanks. function db_userexists($name, $pwd, &$dbErr) { $bUserExists = false; $uid = 0; $dbErr = ''; $db = new mysqli(SERVER, USER, PASSWORD, DB); if (!mysqli_connect_errno()) { $query = "select uid from user where uname = ? and pwd = ?"; $stmt = $db->prepare($query); if ($stmt) { if ($stmt->bind_param("ss", $name, $pwd)) { if ($stmt->bind_result($uid)) { if ($stmt->execute()) { if ($stmt->fetch()) { if ($uid) $bUserExists = true; } } } } if (!$bUserExists) $dbErr = $db->error(); $stmt->close(); } if (!$bUserExists) $dbErr = $db->error(); $db->close(); } else { $dbErr = mysqli_connect_error(); } return $bUserExists; }

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  • C++ creating generic template function specialisations

    - by Fire Lancer
    I know how to specialise a template function, however what I want to do here is specialise a function for all types which have a given method, eg: template<typename T> void foo(){...} template<typename T, if_exists(T::bar)>void foo(){...}//always use this one if the method T::bar exists T::bar in my classes is static and has different return types. I tried doing this by having an empty base class ("class HasBar{};") for my classes to derive from and using boost::enable_if with boost::is_base_of on my "specialised" version. However the problem then is that for classes that do have bar, the compiler cant resolve which one to use :(. template<typename T> typename boost::enable_if<boost::is_base_of(HasBar, T>, void>::type f() {...} I know that I could use boost::disable_if on the "normal" version, however I do not control the normal version (its provided by a third party library and its expected for specialisations to be made, I just don't really want to make explicit specialisations for my 20 or so classes), nor do I have that much control over the code using these functions, just the classes implementing T::bar and the function that uses it. Is there some way to tell the compiler to "always use this version if possible no matter what" without altering the other versions?

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  • Complicated API issue with calling assemblies dynamically?

    - by Stefanos Tses
    I have an interesting challenge that I'm wondering if anyone here can give me some direction. I'm writing a .Net windows forms application that runs on a network and uses an SQL Server to save and pull data. I want to offer a mini "plugin" API, where developers can build their own assemblies and implement a specific interface (IDataManipulate). These assemblies then can be used by my application to call the interface functions and do something. I can create assemblies using my API, copy the file to a folder in my local hard drive and configure my application to use Reflection to call a specific function from the implemented interface (IDataManipulate.Execute). The problem: Since the application will be installed in multiple workstations in the network, is impossible to copy the plugin dlls the users will create to each machine. Solutions I tried: Solution 1 Copy the API dll to a network share. Problem: Requires AllowPartiallyTrustedCallersAttribute, which requires .Net singing, which I can't force from my users. Solution 2 (preferred) Serialize the dll object, save it to the database, deserialize it and call IDataManipulate.Execute. Problem: After deserialization, I try cast it to a IDataManipulate object but returns an error looking for the actual dll file. Solution 3 Save the dll bytes as byte[] to the database and recreate the dll at the local PC every time the user starts my application. Problem: Dll may have dependencies, which I don't know if I can detect. Any suggestions will be greatly appreciated. Thanks

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  • PHP sleep() excution sequence while echoeing.

    - by Babiker
    I have the following: echo time()."<br>"; sleep(1); echo time()."<br>"; sleep(1); echo time()."<br>"; I wrote the preceding code with intention to echo time()."<br>" ln 1,echo time()."<br>" ln 4, wait a final second and then echo the final time()."<br>". Altough the time bieng echoed is correct when it comes to the intervals between time(), all echo functions are echoeing after the total of the waiting period/parameters in each sleep function. This is how the script runs: Excutes. Waits 2 secons. echoes 1275540664 1275540665 1275540666 Notice the correct incrementation in time() being echoed. My question is why is it not behaving like expected to where it echoes, waits a second, echoes again, waits one final second and then echos the last parameter? I know my question is a little confusing due to my wording, but i will try my hardest to answer any comments regarding this, thanks.

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  • Making alarm clock with NSTimer

    - by Alex G
    I just went through trying to make an alarm clock app with local notifications but that didn't do the trick because I needed an alert to appear instead of it going into notification centre in iOS 5+ So far I've been struggling greatly with nstimer and its functions so I was wondering if anyone could help out. I want when the user selects a time (through UIDatePicker, only time) for an alert to be displayed at exactly this time. I have figured out how to get the time from UIDatePicker but I do not know how to properly set the firing function of nstimer. This is what I have attempted so far, if anyone could help... be much appreciated. Thank you Example (it keeps going into the function every second opposed to a certain time I told it too... not what I want): NSDate *timestamp; NSDateComponents *comps = [[[NSDateComponents alloc] init] autorelease]; [comps setHour:2]; [comps setMinute:8]; timestamp = [[NSCalendar currentCalendar] dateFromComponents:comps]; NSTimer *f = [[NSTimer alloc] initWithFireDate:timestamp interval:0 target:self selector:@selector(test) userInfo:nil repeats:YES]; NSRunLoop *runner = [NSRunLoop currentRunLoop]; [runner addTimer:f forMode: NSDefaultRunLoopMode];

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  • Why should I abstract my data layer?

    - by Gazillion
    OOP principles were difficult for me to grasp because for some reason I could never apply them to web development. As I developed more and more projects I started understanding how some parts of my code could use certain design patterns to make them easier to read, reuse, and maintain so I started to use it more and more. The one thing I still can't quite comprehend is why I should abstract my data layer. Basically if I need to print a list of items stored in my DB to the browser I do something along the lines of: $sql = 'SELECT * FROM table WHERE type = "type1"';' $result = mysql_query($sql); while($row = mysql_fetch_assoc($result)) { echo '<li>'.$row['name'].'</li>'; } I'm reading all these How-Tos or articles preaching about the greatness of PDO but I don't understand why. I don't seem to be saving any LoCs and I don't see how it would be more reusable because all the functions that I call above just seem to be encapsulated in a class but do the exact same thing. The only advantage I'm seeing to PDO are prepared statements. I'm not saying data abstraction is a bad thing, I'm asking these questions because I'm trying to design my current classes correctly and they need to connect to a DB so I figured I'd do this the right way. Maybe I'm just reading bad articles on the subject :) I would really appreciate any advice, links, or concrete real-life examples on the subject!

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  • Within a DLL, how is the function table structured?

    - by Willi Ballenthin
    I've been looking into the implementation of a device library that doesn't explicitly support my operating system. In particular, I have a disassembled DLL, and a fair amount of supporting source code. Now, how is the function table/export table structured? My understanding is that the first structure of the .data section is a table of VRAs. Next is a table of strings linked by index to that first address table. This makes sense to me, as a linker could translate between symbols and addresses. How do functions referenced by ordinals fit into this picture? How does one know which function has such and such ordinal number, and how does the linker resolve this? In other words, given that some other DLL imports SOME_LIBRARY_ordinal_7, how does the linker know which function to work with? Thanks, all! edit More information... Im working with the FTDI libraries, and would like to resolve which function is being invoked. In particular, I see something like: extern FTD2XX_Ordinal_28: near how might I go about determining which function is being referenced, and how does the linker do this?

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  • Passing System classes as constructor parameters

    - by mcl
    This is probably crazy. I want to take the idea of Dependency Injection to extremes. I have isolated all System.IO-related behavior into a single class so that I can mock that class in my other classes and thereby relieve my larger suite of unit tests of the burden of worrying about the actual file system. But the File IO class I end up with can only be tested with integration tests, which-- of course-- introduces complexity I don't really want to deal with when all I really want to do is make sure my FileIO class calls the correct System.IO stuff. I don't need to integration test System.IO. My FileIO class is doing more than simply wrapping System.IO functions, every now and then it does contain some logic (maybe this is the problem?). So what I'd like is to be able to test my File IO class to ensure that it makes the correct system calls by mocking the System.IO classes themselves. Ideally this would be as easy as having a constructor like so: public FileIO( System.IO.Directory directory, System.IO.File file, System.IO.FileStream fileStream ) { this.Directory = directory; this.File = file; this.FileStream = fileStream; } And then calling in methods like: public GetFilesInFolder(string folderPath) { return this.Directory.GetFiles(folderPath) } But this doesn't fly since the System.IO classes in question are static classes. As far as I can tell they can neither be instantiated in this way or subclassed for the purposes of mocking.

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  • Flowcharting functional programming languages

    - by Sadface
    Flowcharting. This ancient old practice that's been in use for over 1000 years now, being forced upon us poor students, without any usefulness (or so do I think). It might work well with imperative, sequentially running languages, but what about my beloved functional programming? Sadly, I'm forced to create a flow chart for my programm (that is written in Haskell). I imagine it being easy for something like this: main :: IO () main = do someInput <- getLine let upped = map toUpper someInput putStrLn upped Which is just 3 sequenced steps, fetching data, uppercasing it, outputting it. Things look worse this time: main :: IO () main = do someInput <- fmap toUpper getLine putStrLn someInput Or like this: main :: IO () main = interact (map toUpper) Okay, that was IO, you can handle that like an imperative language. What about pure functions? An actual example: onlyMatching :: String -> [FilePath] -> [FilePath] onlyMatching ext = filter f where f name = lower ('.' : ext) == (lower . takeExtension $ name) lower = map toLower How would you flowchart that last one?

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